Molybdenum is obtained as a by-product of copper mining or is mined directly (primary deposits are in the Rocky Mountains in Colorado). In both cases, it is obtained as MoS₂, which is then converted to MoO₃. The MoO₃ can be used directly in the production of stainless steel for high-speed tools (which accounts for about 85% of the molybdenum used). Molybdenum can be purified by dissolving MoO₃ in aqueous ammonia and crystallizing ammonium molybdate. Depending on conditions, either (NH₄)₂Mo₂O₇ or (NH₄)₆Mo₇O₂₄⋅₄H₂O is obtained. Give names for MoS₂ and MoO₃.